SYNTHESIS AND STRUCTURE OF THE PEROVSKITE OXY-SULFATES BA4MCU2+XO6+Y(SO4)Z (M=CA, Y)

The synthesis and structures of perovskite oxy-sulphates of the form B a4MCu2+xO6+y(SO4)z (M = Ca, Y) are reported. The basic structure consi sts of an ordered arrangement of M and Cu on the small cation sites, w ith three unique Cu sites. Two of the Cu sites are fully occupied, whe reas the third contains a small amount of vacancies and is also partia lly occupied by the S of a sulphate group. The orientation of the sulp hate groups in the structure is shown to vary with sample composition, and comparisons are made with the corresponding oxy-carbonates report ed previously.